Avoiding Mistakes in Electric Fleet Operations

Recently, a warehouse operations manager called with a weekend emergency. “The entire bank of chargers is down, we won’t have any way to charge our warehouse truck batteries.” The usual questions were asked: AC power, fuses OK? “Yes.” Any known power surges/lightning strike damage? “No.” Chargers moved and reconnected in a new location or to a different AC input voltage? Any connector work done on the output cables? “No.”

Electricians were there at the scene to help sort out the problem, but they were flying blind, being unfamiliar with battery chargers. All AC fuses checked out OK, but “Each charger seems to have a single odd fuse blown. One that the electricians don’t have.” That would be the DC output fuse designed to protect the charger diodes from unusual currents, particularly reverse polarity currents.

Anything done to the batteries recently? “We did have an outside lift truck maintenance service come in and do some limited truck work; they just installed some new connectors on lift trucks and a couple of batteries.” Yep. At least one of those batteries must now have the connector on backwards, I told him.

The initial attempt at plugging that backwards battery into a charger would have resulted in blowing the charger’s DC fuse, instantly disabling it. The rest would have been up to the operator. Discovering that the charger was “bad”, the lift truck operator may have tried the next charger in line, instantly blowing its DC fuse, then the next, until he discovered he had a whole charging rack full of “bad” chargers. This is a disaster for a warehouse in the busy season. I hope the truck maintenance service was a bargain, because situations like this can cost an operation money.

The lesson that can be learned here is to make changes, upgrades, and repairs in an electric fleet system with care. The best and biggest advantage to using electric lift trucks is the outstandingly low cost of operation and maintenance, so one can afford to take reasonable care during rare repair situations.

The most common upgrade path involves bringing in new lift trucks and/or new batteries. If a charging crunch at the end of the shift is not a problem with the new addition (enough chargers to go around), one still has to be careful to see that the chargers have the appropriate rating for the new battery size. Remember that a forklift battery has two significant operating specifications: voltage and capacity (commonly stated Ampere hours). A higher capacity battery requires a charger rated appropriately higher, and some special high-performance batteries with very strong electrolyte (high specific gravity, 1,300+ at full charge) must have a charger with an elevated finish rate, as well.

The newest, and most severe, charger incompatibility situation involves bringing a sealed “maintenance-free” battery into an existing fleet. No charger set up for standard “flooded” lead-acid batteries can be used to charge a sealed battery (some advanced chargers can be adjusted, but this is usually not a toggle-switch changeover). In many cases, charging a sealed battery just one time on a standard charger may damage the battery irreparably. This means that special precautions are necessary to avoid using the wrong charger in a mixed fleet that includes any sealed batteries.

Color-keyed connectors can be a first step in making a mixed battery fleet work (the popular Anderson SB style connector is notched to mate only matching connectors), but that presumes that no one in the operation sidesteps this control by notching out connectors with a pocket knife to make them universal. It happens. The best way to protect your investment might be to: A) Don’t have a mixed fleet, or B) Use an entirely different connector style for the odd battery/charger combination. Keep in mind that since the lift truck connector must match the battery, you are limiting the truck(s) with the sealed battery to just that battery type alone.

For more information, contact Arcon Equipment Inc. (440) 232-1422.